In general, ink jet printing machines or printers include at least one printhead that ejects drops or jets of liquid ink onto a recording or image forming media. A phase change ink jet printer employs phase change inks that are in the solid phase at ambient temperature, but transition to a liquid phase at an elevated temperature. The molten ink can then be ejected onto a printing media by a printhead directly onto an image receiving substrate, or indirectly onto an intermediate imaging member before the image is transferred to an image receiving substrate. Once the ejected ink is on the image receiving substrate, the ink droplets quickly solidify to form an image.
In both the direct and offset printing architecture, images may be formed on a media sheet or a media web. In a web printer, a continuous supply of media, typically provided in a media roll, is mounted onto rollers that are driven by motors. A loose end of the media web is passed through a print zone opposite the print head or heads of the printer. Beyond the print zone, the media web is gripped and pulled by mechanical structures so a portion of the media web continuously moves through the print zone. Tension bars or rollers may be placed in the feed path of the moving web to remove slack from the web so it remains taut without breaking.
Some direct marking, continuous web printers are configured to print images onto both sides of the web, also referred to as duplex printing. To enable duplex printing on a continuous web, a web transport system may be configured to print onto one side of the web and direct the web back through an inversion system that inverts, or flips, the web over so that the opposite side is facing the print zone. To invert the web for duplex printing, some previously known systems utilized fixed turn bars that invert the web after printing one side (e.g., simplex side), and laterally offset the web to direct the web to the entrance of the duplex web path for printing on the other side (duplex side), all without active registration. Typical setups strive to maintain alignment of the web as it enters and exits the turn bars. Making the exit turn bar adjustable may effectively change the lateral registration of the web. However, adjusting the position of the exit turn bar alters the web path length which, as mentioned above, can affect web tension to cause loss of web control, web damage, or breakage. In other previously known systems, a bias roller with a manually adjusted edge guide has also been used to laterally register the return path web, but it is known to generate loose paper dust and fibers that may contaminate the printheads, thus reducing image quality and printhead life.